1. Field of the Invention
The present invention relates to an equalizer for a digital video disk player (DVDP), and in particular, to an improved equalizer for a DVDP which is capable of obtaining a 5-tap transversal filter effect by providing a 3-tap transversal filter which is used for a DVD-P, a DVD-ROM, etc.
2. Description of the Conventional Art
Conventionally, the equalizer is used for wave-shaping an RF (Radio Frequency) signal obtained by an optical pickup apparatus, processing a signal amplitude of a low level and high frequency such as, by way of example, (where T=33.3 nsec), 4T, or 5T, and increasing the entire gain, thus improving any signal interference and jitter problem.
Therefore, more accurate EFM (Eight- Fourteen Modulation) data is obtained using the equalizer.
FIG. 1, which is labeled prior art, is a view illustrating a conventional 5-tap construction. As shown therein, the RF signal flows through four delay lines composed of a T-structure. In this arrangement, the output signal from an equalizer is obtaining by multiplying the output signal from each delay unit and the coefficient C and adding the same.
In addition, the transfer characteristic of the above-described prior art construction may be expressed as the following Equation 1: EQU G.sub.5 (Z)=Z.sup.-2 -C(1+Z.sup.-1 +Z.sup.-3 +Z.sup.-4)
where G.sub.5 denotes a transfer function of a transversal filter when configuring the 5-tap construction, and Z denotes a delay function.
In a DVDP specification, it is recommended to use a 5-tap transversal filter type equalizer. However, an equalizer chip which is capable of performing a 5-tap function has not yet developed.
Therefore, in order to implement the above-described 5-tap transversal filter, the delay line and modules have been designed to use a separate discrete device such as a resistor, condenser, arithmetic operation amplifier, etc.
Namely, it is difficult to fabricate a delay unit of more than 100 nsec using one filter. In addition, it is difficult to obtain a short delay time by connecting in series the same. The above-described problem occurs due to the impedance matching problem before and after the delay device and the noise of the devices.
Therefore, there has been a need to develop a method by which it is possible to minimize the number of elements for a digital video disk player, thus performing a 5-tap function.